“Flexible Working Hours involve a continuous choice on behalf of employers, employees or both, regarding the amount (chronometry) and the temporal distribution (chronology) or working hours” (Janssen & Nachreiner, p. 12).
“Workplace flexibility is the ability of workers to make choices influencing when, where, and for how long they engage in work-related tasks” (Hill, et al., p. 159).

Janssen, D. & Nachreiner, F. (2004). Health and psychosocial effects of flexible working hours. Revista de Saude Publica, 38(suppl), 11-18. Hill, E.J., Grzywacz, J.G., Allen, S., Blanchard, V.L., Matz-Costa, C., Shulkin, S., & Pitt-Catsouphes, M. (2008). Defining and conceptualizing workplace flexibility. Community, Work, and Family, 11, 149-163.